JP5254820B2 - COMMUNICATION DEVICE, COMMUNICATION SYSTEM, AND COMMUNICATION METHOD - Google Patents

Description

  The present invention relates to a communication system and a communication method, and particularly to a technique for effectively preventing interception.

For example, measures against anti-interception using radio are slightly different between voice communication and information communication. However, when voice communication is digitized, the method is generally the same. That is, in the case of voice, the voice is digitized, the digital data is encrypted, and modulated by a modulation method determined by the communication method, and at reception, it is demodulated using a demodulation method corresponding to the modulation method, Based on cryptographic synchronization, the cipher can be broken according to a predetermined algorithm. In this case, since the communication speed is also determined, the symbol rate is the same for transmission and reception.
In such processing, whether or not interception is possible depends on the encryption strength of the encryptor.

  Further, as another method of anti-interception measures, for example, there is a spread spectrum method. That is, by performing primary modulation (data modulation) and secondary modulation (spreading modulation), interference resistance and interception resistance can be achieved.

JP 2002-232393 A

However, with regard to anti-interception measures, there are still insufficient points, and further development has been required.
The present invention has been made in view of such a conventional situation, and an object thereof is to provide a communication system and a communication method that can effectively prevent interception.

In order to achieve the above object, in the present invention, a communication apparatus that allocates and transmits data to a plurality of subcarriers has the following configuration.
That is, in a communication apparatus that allocates and transmits data to a plurality of subcarriers, first code sequence generation means for generating a random code sequence and a code sequence generated by the first code sequence generation means And an order changing means for changing an order of assigning data to the subcarriers.
In the present invention, the following configuration is adopted in a communication system that allocates and transmits data to a plurality of subcarriers.
That is, in a communication system in which data is allocated to a plurality of subcarriers and transmitted, a transmission side generates a random code sequence, a transmission side code sequence generation unit, and a code sequence generated by the transmission side code sequence generation unit Transmitting side order changing means for changing the data allocation order to the subcarrier based on the receiving side, the receiving side code sequence generating means identical to the transmitting side code sequence generating means, and the subcarrier Receiving side sequence changing means for returning the data allocated to the original sequence based on the code sequence generated by the receiving side code series generating means.

Here, various numbers may be used as the number of the plurality of subcarriers.
Various random code sequences may be used.
In addition, for a value obtained by multiplying one symbol length by an integer, various magnifications may be used as an integer multiple.
Further, the change time of the data allocation order to the subcarriers is calculated, for example, in units of symbol length.
In addition, various methods may be used as an order of assigning data to a plurality of subcarriers (assignment order) and a method for changing the order.

  Moreover, as a random code sequence used when calculating the change time of the allocation order of data to subcarriers and a random code sequence used when changing the allocation order of data to subcarriers, as an example A common one is used, but a different one may be used as another example.

Also, in the present invention, the following configuration is adopted in the communication method for allocating and transmitting data to a plurality of subcarriers.
That is, in a communication method for allocating and transmitting data to a plurality of subcarriers, a random code sequence is generated on the transmission side, the data allocation order to the subcarriers is changed based on the code sequence, and the reception side The same random code sequence as that on the transmission side is generated, and the data allocated to the subcarriers is returned to the original arrangement based on the code sequence.

  As described above, according to the present invention, when data is allocated to a plurality of subcarriers and transmitted, the data allocation order to the subcarriers is changed and the allocation order is changed based on a random code sequence. Since the time (change time) to control is controlled, interception can be effectively prevented.

It is a figure which shows the structural example of the transmission / reception station which concerns on one Example of this invention. It is a figure for demonstrating the generation method of a time-axis. It is a figure for demonstrating an example of the allocation method of the digital data with respect to a frequency axis, and the series of the information after a demodulation. It is a figure which shows an example of the arrangement | sequence of the digital data which combined the time-axis generation | occurrence | production and the frequency axis. It is a figure which shows an example of the comparison with the arrangement | sequence of the digital data of this system, and the arrangement | sequence of the original digital data. It is a figure which shows an example of a general communication system. It is a figure which shows the structural example of the transmission system (transmitter) of digital communication. It is a figure which shows the structural example of the receiving system (receiver) of digital communication.

Embodiments according to the present invention will be described with reference to the drawings.
First, the background art will be described with reference to FIGS.
FIG. 6 shows an example of a general communication system.
In the communication system of this example, two transmitting / receiving stations 21 and 22 and two intercepting stations 31 and 32 are shown. The two transmission / reception stations 21 and 22 are original transmission and reception counterparts (communication counterparts), and the contents of the communication are not desired to be acquired by the interception stations 31 and 32. Here, each transmitting / receiving station 21 and 22 has a transmission function and a reception function.

However, it is possible to detect the frequency of the radio wave, and stations (interception stations 31, 32) that acquire the communication contents can be generated in accordance with the frequency. Since such a station is not an original communication partner, it is expressed as an interceptor station.
Usually, the frequency and modulation method can be received together with the demodulation method by analyzing. For this reason, in order to make the interception impossible, the digital data must be encrypted, and whether or not the interception is possible depends on the encryption strength.

FIG. 7 shows a configuration example (an example of a transmission system) of a digital communication transmission system (transmitter).
The transmission system of this example includes an encoder 41, a modulation unit (in this example, a digital modulator) 42, and a transmission unit 43.
The digital information c1 to be sent is input to the encoder 41. The encoder 41 performs error correction coding, interleaving, addition of a frame synchronization code, addition of a control code necessary for control of the communication system, and the like on the input digital information c1, and the digital information on which these are performed. The signal c2 is output to the modulation unit 42.

The modulation unit 42 performs modulation to convert the input digital signal c <b> 2 into an analog signal and outputs the modulation signal c <b> 3 to the transmission unit 43. Here, in the digital communication system, the modulation unit 42 is configured using a digital modulator. As a modulation method of such a modulator, there are PSK (Phase Shift Keying), FSK (Frequency Shift Keying), QAM (Quadrature Amplitude Modulation) and the like.
The transmission unit 43 converts the input modulated signal c3 into a signal having a transmission frequency, amplifies it to a required power, and then radiates it as a radio wave from an antenna (not shown).

FIG. 8 shows a configuration example (reception system example) of a digital communication reception system (receiver).
The receiving system of this example includes a receiving unit 51, a demodulating unit (in this example, consisting of a digital demodulator) 52, and a decoder 53.
Received radio waves (received signals) are input to the receiving unit 51. The receiving unit 51 amplifies the received signal to a required level and outputs the amplified signal d1 to the demodulating unit 52.

The demodulator 52 performs demodulation to convert the input amplified signal d1 into a digital signal, and outputs the digital signal d2 to the decoder 53. Here, in the digital communication system, the demodulator 52 is configured using a digital demodulator.
The decoder 53 detects a control code necessary for control of the input digital signal d2, performs control necessary for control of the communication system, and thereafter performs processing such as synchronization code detection, deinterleaving, and error correction. After that, the final reception process is performed and output as digital information d3.

Next, a configuration characteristic of this example will be described.
FIG. 1 shows a configuration example of a transmission system (transmitter) and a configuration example of a reception system (receiver) as a configuration example (an example of a communication system) of a transmission / reception station in a digital communication system according to an embodiment of the present invention. A configuration example is shown.
The transmission system of this example includes an encoder 1, a modulation unit (consisting of a digital modulator in this example) 2, a transmission unit 3, a random code generation unit F4, and a random code generation unit T5.
The reception system of this example includes a reception unit 11, a demodulation unit (in this example, a digital demodulator) 12, a decoder 13, a random code generation unit F14, and a random code generation unit T15.

Here, in this example, as a modulator of the modulation unit 2 and a demodulator of the demodulation unit 12, a digital modulator such as OFDM (Orthogonal Frequency Division Multiplexing) -2 phase, 4 phase, 8 phase, 16 QAM, 32 QAM, 64 QAM, etc. Or use a digital demodulator.
In this example, digital modulation and digital demodulation such as OFDM-2 phase, 4 phase, 8 phase, etc., 16QAM, 32QAM, 64QAM, etc. are 2 phases in each of a plurality of carriers (subcarriers) in the OFDM modulation system. Modulation schemes such as 4-phase, 8-phase, 16QAM, 32QAM, and 64QAM are used. A random code generator F and a random code generator T necessary for the transmission system and the reception system are used in the present invention. The codes used for OFDM frequency axis allocation and time axis change are F for transmission. And F for reception have the same configuration, and T for transmission and T for reception have the same configuration.

An example of the operation performed in the transmission system of this example is shown.
The digital information a1 to be sent is input to the encoder 1. The encoder 1 performs error correction coding, interleaving, addition of a frame synchronization code, addition of a control code necessary for control of the communication system, and the like on the input digital information a1, and the digital information in which these are performed. The signal a2 is output to the modulation unit 2.

The modulation unit 2 is composed of a digital modulator such as OFDM and PSK, FSK, QAM. Usually, the subcarrier (OFDM) allocation order of the digital signal a2 (signal sequence) is fixed, but in the case of the present invention, it is determined by the signal from the random code generator F4. Further, the random code generator T5 is used to change the random code sequence on the time axis (an appropriate multiple of symbols), and digital information is exchanged on both the time axis and the frequency axis. The modulation unit 2 modulates the input signal a2 and outputs the modulation signal a3 to the transmission unit 3.
The transmitter 3 converts the input modulated signal a3 into a signal having a transmission frequency, amplifies the signal to a required power, and then radiates it as a radio wave from an antenna (not shown).

An example of the operation performed in the receiving system of this example will be shown.
Received radio waves (received signals) are input to the receiving unit 11. The reception unit 11 amplifies the reception signal to a required level and outputs the amplified signal b1 to the demodulation unit 12.
After demodulating the received signal for each subcarrier, the demodulator 12 switches the order of the random code generator F14 and the order specified by the random code generator T15, and sends the digital signal b2 obtained thereby to the decoder 13. Output. After that, the decoder 13 detects and removes control codes necessary for error correction coding, deinterleaving, frame synchronization detection, and other communication system control, and then outputs received data b3.
At this time, the transmission random code generation unit F4 and the reception random code generation unit F14, and the transmission random code generation unit T5 and the reception random code generation unit T15 are synchronized by transmission / reception of other signals prior to communication. I will do it.

  The decoder 13 detects a control code necessary for control of the input digital signal b2 and performs control necessary for control of the communication system. After performing the processing, the final reception processing is performed and output as digital information b3.

With reference to FIG. 2 to FIG. 5, a method for preventing interception in the transmission / reception station of this example will be described.
In this example, a case where OCC (One Coincidence Code) having a sequence length of 6 bits is used for generation of a time axis and generation of a frequency axis is shown.

Here, in this example, the code generated in the common OCC is used for both the time axis and the frequency axis. However, the same code is not applied to both the time axis and the frequency axis at the same time, but the same code as a whole. Although it is a series, each code is applied separately to the time axis and the frequency axis.
Specifically, with respect to the frequency axis, information to be assigned to each of n (n is a numerical value) is determined based on the OCC code. In this example, six carriers are determined. The information to be assigned (for example, the order in which each data value of the target data series is assigned) is switched so as to correspond to 6-bit OCC. Also, for the time axis, the time for continuing the same information allocation state for the frequency axis described above (in this example, the time in symbol units) is determined based on the OCC code, and for each OCC value, The time corresponding to the value (in this example, the number of symbols determined from the value) is determined.
In this example, the information allocation operation regarding the frequency axis and the time axis is performed on the transmission side, and the reception side performs original information (the operation is performed on the transmission side from the received signal in accordance with the operation on the transmission side. Get previous information). In this example, the receiving side has the same OCC function as that of the transmitting side. For example, using the OCC code generated in synchronization with the transmitting side, the receiving side performs the reverse operation of the transmitting side. Information can be acquired.

A method for generating a time axis will be described with reference to FIGS.
In this example, OCC, which is a special random code sequence, is used as a code for determining the length of the time axis.
FIG. 2A shows an example of the generated code. In this example, 6 bits are used as the length of the code word.
FIG. 2B shows a multiple M of the time axis. In this example, M is an integer of 1 or more.
FIG. 2C shows the basic unit length B. In this example, the basic unit length B is a multiple of the symbol length (N times), that is, B = (1 symbol length × N). N is an integer greater than or equal to 1, and in this example, N = 2.
FIG. 2D shows the length of the final time axis when using the above-described FIGS. 2A, 2B, and 2C (in symbol units, that is, how many times one symbol) Is shown.

Specifically, in the example of FIG. 2A, when the first sequence is (1, 2, 3, 4, 5, 6), the next sequence is (5, 3, 1, 6, 4, 2).
2D, the final length of the time axis is 2 symbols, 4 symbols, 6 symbols,... From the beginning. That is, (M × B) = (M ×) obtained when M = (1, 2, 3, 4, 5, 6), (5, 3, 1, 6, 4, 2),. N) [Symbol length].

With reference to FIGS. 3A to 3D, an example of a digital data allocation method (allocation state) for a frequency axis (subchannel) and an information sequence after demodulation will be described.
In the example of FIG. 3A, the vertical axis represents the frequency channel.
Usually, digital data is allocated as shown by a dotted line (1). That is, as shown in one row (repetition of this), in the case of the present invention, as shown in two columns, three columns,... This state is shown in (B), (C), and (D). (B) shows the jump destination channel in which the dotted line order of (A) is arranged horizontally. As a result, the state (C) is obtained in the space. The numbers a1, a2,... In the symbol (C) indicate the original subchannel state. (D) returns to the original arrangement according to the sequence of the received random code generator F14. This state is shown in (D). Thus, in reception (D), the state returns to the original state as in the original subchannel state, that is, 1, 2, 3,.

  Also, as an example, the use / non-use of the used subchannel is specified from the receiving side. Specifically, the quality of the subchannel is determined on the receiving side based on the equalization error, and the unused subchannel number is not used. Send information to the sender. The transmitting side sends a dummy signal on an unused subchannel, and the receiving side removes the subchannel. For these reasons, the subchannel that is disturbed is not used.

FIG. 4 shows an example of an array of digital data in which the time axis generation and the frequency axis are combined.
The horizontal direction represents the time direction, and (1) in the drawing represents the length of the time axis (length in symbol units), and (2) represents the frequency axis. Each time axis has the same arrangement in the frequency direction. Specifically, the arrangement of the information allocation in the frequency direction continues to be the same for the length of 2 symbols at the beginning, then for the length of 4 symbols, and then for the length of 6 symbols. In the meantime, in the respective continuation times, the same information arrangement continues in the frequency direction.
FIG. 5 shows an example of comparison between the digital data array of this system and the original digital data array.

  In the method of this example, even if the frequency is known, the modulation / demodulation method is changed over time, and even if the radio wave is received, it cannot be demodulated to the original digital data. , Interception can be impossible. Normally, when digital data is also encrypted, it is possible to construct a communication system having stronger protection.

  In this example, specifically, in a communication system using modulation schemes such as OFDM-2 phase, 4 phase, 8 phase, etc., 16QAM, 32QAM, 64QAM, etc., use / nonuse of each subcarrier and subcarrier The arrangement order on the frequency axis of the digital data in the case of modulation is changed based on a special random code sequence (OCC code in this example). This arrangement order is switched at an integer multiple of the symbol rate, and the value of the integer multiple is also determined using the special random code sequence described above. On the reception side, correct digital data is decoded by synchronizing the special random code sequence for switching on the time axis and changing the combination on the frequency axis.

  As described above, in this example, in a communication system (or communication method) that allocates and transmits data to a plurality of subcarriers, a function (or processing step) for generating a random code sequence, and the random code A function (or processing step) for calculating a subcarrier switching time by multiplying a sequence by a value obtained by multiplying a symbol length by an integer, and changing a data allocation order to the subcarriers based on the random code sequence Function (or processing step).

Specifically, the time axis (multiple of symbols) and the frequency axis are determined by modulation of OFDM (for example, using a modulation system such as 2 phase, 4 phase, 8 phase, etc., 16QAM, 32QAM, 64QAM, etc.). Switch according to the specified rules and send.
In reception, reception is performed by switching the time axis and the frequency axis based on the rules described above.
Switching on the time axis is performed at a multiple of the symbol rate, and the multiple is set to an appropriate length. Based on the appropriate length, the basic length is a random code sequence with regularity.
Normal symbols are used for switching symbols on the time axis.
With respect to the pattern in which the entire switching as described above is performed, for example, it is performed with a corresponding pattern from the time when a unique synchronization signal of the first sender using this system is detected. All receivers are synchronized based on the clock extracted from the received signal. As a temporal clock in this case, a clock extracted from the received signal is used.
If necessary, auxiliary means such as GPS (Global Positioning System) can be used for time synchronization.

  In this way, in the anti-interception communication method using the OFDM modulation method of this example, in addition to countermeasures against eavesdropping by encryption, for example, by changing the modulation and demodulation parameters conventionally determined by the communication method, reception is performed. Interception resistance can be realized.

  Specifically, for example, OFDM-2 phase, 4 phase, 8 phase, etc., 16QAM, 32QAM, 64QAM etc. and subcarrier use / non-use control, use order (on frequency axis) time (on time axis) By switching by, unnecessary interception can be avoided. Further, by combining the above combination with 2-phase, 4-phase, 8-phase, etc., 16QAM, 32QAM, 64QAM, etc., it is also possible to increase the probability of interception avoidance (that is, make interception more difficult). Moreover, it is also possible to use for multiple access by patterning the frequency axis and the time axis so as not to overlap.

  Note that in the communication system of this example (in this example, the modulation unit 2 of the transmitter shown in FIG. 1), an OFDM modulation method is used as a method of allocating data to a plurality of subcarriers and transmitting the random code. A code sequence generation means is configured by a function for generating a sequence (in this example, an OCC code sequence), and the generated random code sequence (in this example, its value M) is multiplied by one symbol length to an integer multiple. The change time calculation means is configured by the function of calculating the change time (M × N [symbol] in this example) of the allocation order of the data to the subcarriers by multiplying the value (in this example, N times). The order changing means is configured by the function of changing the order of data allocation to the subcarriers (in this example, the order shown in FIGS. 2 to 5) based on the generated random code sequence. To have.

Here, the configuration of the system and apparatus according to the present invention is not necessarily limited to the configuration described above, and various configurations may be used. The present invention can also be provided as, for example, a method or method for executing the processing according to the present invention, a program for realizing such a method or method, or a recording medium for recording the program. It is also possible to provide various systems and devices.
The application field of the present invention is not necessarily limited to the above-described fields, and the present invention can be applied to various fields.
In addition, as various processes performed in the system and apparatus according to the present invention, for example, the processor executes a control program stored in a ROM (Read Only Memory) in hardware resources including a processor and a memory. A controlled configuration may be used, and for example, each functional unit for executing the processing may be configured as an independent hardware circuit.
The present invention can also be understood as a computer-readable recording medium such as a floppy (registered trademark) disk or a CD (Compact Disc) -ROM storing the control program, and the program (itself). The processing according to the present invention can be performed by inputting the program from the recording medium to the computer and causing the processor to execute the program.

  1, 41 .. Encoder, 2, 42 .. Modulator, 3, 43 .. Transmitter, 4, 14 .. Random code generator F, 5, 15 .. Random code generator T, 11, 51.・ Receiver, 12, 52. ・ Demodulator, 13, 53 ・ ・ Decoder, 21,22 ・ ・ Transmission / reception station, 31, 32 ・ ・ Interception station,

Claims (3)

In a communication device that allocates and transmits data to a plurality of subcarriers,
First code sequence generation means for generating a random code sequence;
Order changing means for changing the order of data allocation to the subcarriers based on the code sequence generated by the first code sequence generating means;
Second code sequence generating means for generating a random code sequence;
A duration calculation unit that calculates a duration of the allocation order based on the code sequence generated by the second code sequence generation unit ;
The communication apparatus according to claim 1, wherein the order changing means changes the data assignment order to the subcarriers by switching the code series generated by the first code series generating means based on the duration . The duration calculation means, according to claim 1, characterized in that calculating said to code sequences which are then generated by the second code sequence generating means, said duration is multiplied by the integral multiple value of one symbol length The communication apparatus as described in. Said first code sequence generating means, said a second code sequence generating means, the communication apparatus according to claim 1 or 2, characterized in that the same code sequence generating means.

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